Sequence valve for piggyback IV administration with tube reversal prevention

ABSTRACT

A piggyback IV administration system uses a solenoid actuated sequence valve to control the flow of fluid from a pair of IV fluid sources to the inlet of an IV pump or controller. The sequence valve pinches off a first tube while allowing fluid to flow through the second tube and then, in response to a control signal, changes state so that the second tube is pinched off and fluid can flow through the first tube unimpeded. Improper placement of the first and second tubes within the sequence valve during setup is prevented.

REFERENCE TO COPENDING APPLICATION

This application is a continuation-in-part of application Ser. No.676,020, now U.S. Pat. No. 4,673,389, filed Nov. 29, 1984.

Reference is made to a copending application Ser. No. 676,009, now U.S.Pat. No. 4,673,390, by G. K. Archibald entitled "Multiple Solution IVSystem" filed on Nov. 29, 1984 and assigned to the same assignee.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to administration of intravenous (IV)fluid. In particular, the present invention is an IV administrationsystem which supplies multiple IV solutions or medications atpredetermined intervals to a patient.

2. Description of the Prior Art

It is quite common in IV therapy to give a patient a primary solutionand one or more secondary solutions or medications. The secondary (or"piggyback") medication is usually given several times a day. An exampleis when a patient is on antibiotics. It is desirable to have an IV pumpand a sequencing valve that administers the primary and secondarysolutions sequentially.

In the past, there have been IV pump systems which allow two fluids tobe administered. In these systems, the secondary medication is pumpeduntil the secondary container goes empty, and then the pump switches tothe primary fluid. An example of this type of system is shown in U.S.Pat. No. 4,451,255. This proves to be a substantial burden to hospitalpersonnel, particularly where the secondary medication is requiredseveral times a day. With the prior art systems, the medical personnelmust change secondary medication bags several times each day.

SUMMARY OF THE INVENTION

The present invention is an improved IV administration system which hasa sequence valve which operates on two tubes which are connected betweenthe inlet of an IV control device (e.g. a pump or controller) and a pairof sources of IV fluids. The sequence valve is set to a first state inwhich the first tube is pinched off and the second tube is open. Inresponse to a valve control signal, the sequence valve changes to asecond state in which the second tube is pinched off and the first tubeis open.

With the present invention, it is possible to provide multiple doses ofthe piggyback or secondary solution without having to change thesecondary container. Since the secondary medication is intended to beprovided to the patient only in limited doses, it is important that thepatient not receive multiple doses at one time due to malfunction orimproper setup of the sequence valve.

With the present invention, the accidental reversing of the first andsecond tubes during setup is prevented. In preferred embodiments, thefirst and second tubes have different diameters, and the sequence valvewill accept the two tubes only in specified positions, so that the twotubes cannot be reversed within the valve.

In addition, the present invention preferably includes a tube retainerand a gate which, in conjunction with the moving part or parts of thesequence valve, require a specified setup sequence as the tubes areinserted into the sequence valve. An improper sequence will prevent thevalve from being ready to operate, and results in the indication of anerror condition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic diagram of a preferred embodiment of theIV administration system using the sequence valve of the presentinvention.

FIG. 2 is a front view of the IV pump of FIG. 1.

FIG. 3 is an electrical block diagram of the system of FIG. 1.

FIG. 4 is a front view of a first preferred embodiment of the sequencevalve.

FIG. 5 is a front view of the sequence valve of FIG. 4 with the frontcover removed.

FIG. 6 is a sectional view along section 6--6 of FIG. 5.

FIG. 7 is a top view of the valve of FIG. 4.

FIG. 8 is a front view of a second preferred embodiment of the sequencevalve.

FIGS. 9 and 10 are partial left and right side views of the sequencevalve of FIG. 8.

FIG. 11 is a top view of the sequence valve of FIG. 8 with the tuberetainer pivoted to its open position.

FIG. 12 is an electrical schematic diagram of the sequence valve of FIG.8.

FIGS. 13A-13D are perspective views showing the setup procedure for athird embodiment of the sequence valve.

FIGS. 14A-14D are front views, similar to FIGS. 13A-13D, respectively,of the sequence valve.

FIGS. 15A-15D are top views, similar to FIGS. 13A-13D, respectively, ofthe sequence valve.

FIG. 16 is a perspective view showing positional relationships of a bellcrank, control gate and tube retainer of the sequence valve of FIGS.13A-15D.

FIG. 17 is a sectional view showing the positional relationships of thebell crank, control gate and tube retainer.

FIG. 18 is a sectional view along section 18-18 of FIG. 17.

FIGS. 19A-19C are electrical schematic diagrams illustrating operationof the sensing of bell crank position and presence of the secondarytubing in the sequencing valve.

FIG. 20 shows a perspective view of a fourth embodiment of the sequencevalve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the preferred embodiment shown in FIG. 1, IV administration system 10includes IV pump 12, which pumps fluid from primary solution bag 14 tosecondary (or piggyback) solution bag 16, to a patient (not shown).Sequence valve 18 is connected between bags 14 and 16 and pump 12 toselect one of the bags 14 and 16 for connection to pump 12.

In the particular embodiment shown in FIG. 1, pump 12 is an IV pump suchas the AVI GUARDIAN 400 pump. Pumps of this general type (which aredescribed in U.S. Pat. No. 4,236,880) use a disposable multiple rollingdiaphragm pumping chamber 20 which is inserted into pump 12. Pumpingchamber 20 has an inlet tubing 22 connected at its inlet end, and anoutlet tubing 24 at its outlet end. A drive mechanism within pump 12causes relative movement of two of the rolling diaphragms of pumpingchamber 20 and the operation of two valves to cause fluid to be pumpedfrom inlet tubing 22 through pumping chamber 20 and out through outlettubing 24 to the patient.

In the embodiment shown in FIG. 1, disposable multiple rolling diaphragmpumping chamber 20, inlet tubing 22 and outlet tubing 24 form a part ofa disposable IV administration set which also includes primary spike 26,primary drip chamber 28, primary tubing 30, proximal Y connector 32,primary roller clamp 34, secondary spike 36, secondary drip chamber 38,secondary tubing 40, secondary roller clamp 42, distal Y connector 44,distal tubing 46, needle 48, and distal roller clamp 50.

Primary spike 26 is inserted into the lower end of primary bag 14, andis connected to the upper end of primary drip chamber 28. The lower endof primary drip chamber 28 is connected by primary tubing 30 to one legof proximal Y connector 32.

Similarly, secondary spike 36 is inserted into the lower end ofsecondary bag 16 and is connected to the upper end of secondary dripchamber 38. The lower end of secondary drip chamber 38 is connectedthrough secondary tubing 40 to the second leg of proximal Y connector32. The third leg of Y connector 32 is connected to inlet tubing 22.

Primary tubing 30 and secondary tubing 40 pass through sequence valve18, and at least one (preferably primary tubing 30) supports sequencevalve 18. In the preferred embodiment of the present invention, sequencevalve 18 is a light-weight, solenoid actuated device which initiallypinches off primary tubing 30 to prevent flow from primary bag 14 whilepermitting flow from secondary bag 16 to pumping chamber 20. In responseto a valve control signal received from pump 12 through multiconductorcable 52, sequence valve 18 switches so that secondary tubing 40 ispinched off and primary tubing 30 is unobstructed. When secondary tubing40 is unobstructed and primary tubing 30 is pinched off, secondary(piggyback) bag 16 is connected to inlet tubing 22, and pump 12 pumpsthe secondary medication from piggyback bag 16 to the patient.Conversely, when secondary tubing 40 is pinched off and primary tubing30 is unobstructed, the primary solution is pumped from primary bag 14to the patient by IV pump 12.

At the outlet end, outlet tubing 24 is connected through distal Yconnector 44 to distal tubing 46. At the end of distal tubing 46 isneedle 48, which is inserted into a vein of the patient. Distal Yconnector 44 has another leg which is normally closed, but which allowsthe insertion of a syringe needle to introduce medication directly intodistal tubing 46 as fluid is being pumped to the patient.

Roller clamps 34, 42 and 50 are used by medical personnel during theinstallation of the IV administration set into pump 12, during initialset-up, and during removal of the IV administration set.

FIG. 2 shows a front view of pump 12. Pump 12 includes a housing 54which contains the electrical control circuitry and the mechanicalportions of the pump which interact with disposable pumping chamber 20.Pump 12 is supported on an IV stand or pole (not shown) by pole clamp56. Door 58 covers a receptacle into which disposable pumping chamber 20is inserted. In the embodiment shown in FIG. 2, the opening of door 58requires operation of the three separate devices: load control handle60, door lock 62, and door latch 64. During normal operation, when theIV administration set is installed with pumping chamber 20 within thereceptacle of pump 12, door 58 is closed as shown in FIG. 2.

In the lower left corner of the front of pump 12 is control panel 66,which includes a keyboard formed by numerical key pads ("0" through"9"), operate key pad (OPR) 68, standby key pad (STBY) 70, PRIMARYindicator 72, PRIMARY-PIGGYBACK toggle key pad 73, PIGGYBACK indicator74, RATE key pad 76, volume limit (LIMIT) key pad 78, and volume infusedclear (CLEAR) key pad 80. Control panel 66 also includes three digitaldisplays: rate display 82, volume limit display 84, and volume infuseddisplay 86.

Pump 12 also includes indicator panel 88 (which provides visualindication of different error or alarm conditions), and audio alarmannunciator 90.

FIG. 3 is an electrical block diagram of pump 12 and sequence valve 18,which are connected together by multiconductor cable 52 and connector92. Sequence valve 18 receives a valve control signal from pump 12, andprovides a valve state signal, which indicates which fluid line (primarytubing 30 or secondary tubing 40) is occluded.

The operation of pump 12 is controlled by pump control 94, which inpreferred embodiments includes a microcomputer, together with associatedmemory, timing and clock circuitry and appropriate interface circuitry.Pump control 94 receives input signals from control panel 66, fromsensor 96 (which sense various operating conditions or parameters suchas output pressure, air bubbles in the IV administration set, empty bagsand opening of door 58), and from sequence valve 18. Pump control 94provides outputs to displays 82, 84 and 86 of control panel 66,indicator panel 88, audio annunciator 90 and to pump drive motor 98. Inaddition, when sequence valve 18 is connected to pump 12 and a piggybackoperation has been selected, pump control 94 provides the valve controlsignal to sequence valve 18.

Control panel 66 allows the medical personnel to "set up" an IVadministration schedule so that predetermined volumes of the primary andsecondary solutions are delivered at predetermined rates. Pump control94 controls the operation of both sequence valve 18 and pump drive motor98, so that it controls both the particular solution being pumped at anygiven time, and the rate at which the fluid is being pumped.

By depressing STBY key pad 70, the medical personnel places pump 12 in astandby mode. This allows changing or resetting of both rates and volumelimits for both the primary and piggyback solutions. The primarysolution rate is selected by depressing PRIMARY-PIGGYBACK toggle key pad73 (toggling to the PRIMARY MODE) and then RATE key pad 76, followed bythe keys representing the numerical value desired. The primary volumelimits can then be set by pressing LIMIT key pad 78 and then using thenumerical keys to enter the desired numerical limit for the primarysolution.

For the piggyback or secondary solution PRIMARY-PIGGYBACK toggle key pad73 is pressed to toggle to the PIGGYBACK mode. RATE key pad 76 is thenpressed, followed by appropriate numerical keys to enter the piggybackrate. LIMIT key pad 78 is then depressed, followed by selected numericalkey pads to set the piggyback volume limit.

Pump control 94 stores the rates and volume limits entered for both theprimary solution and the piggyback solution. These stored values areused, together with an accumulated volume infused value is controllingsequence valve 18 as well as pump drive motor 98.

Sequence valve 18 of the present invention is a spring loaded, solenoidactuated device which initially occludes primary tubing 30 so that thesecondary solution is pumped first. Sequence valve 18 is placed in thisinitial condition by inserting primary tubing 30 into one slot ofsequence valve 18 and then cocking lever 100 so that primary tubing 30is occluded. Secondary tubing 40 is then inserted into an adjacent slotalongside primary tubing 30 in sequence valve 18 as shown in FIG. 1.

Operation of pump 12 in the piggyback mode is initiated by depressingOPR key pay 68. Pump control 94 provides pump drive control signals topump drive motor 98 which cause motor 98 to produce the pumping ratestored for the piggyback solution. As pump drive motor 98 is operated,pump control 94 maintains an accumulated value which represents theamount of secondary solution which has been pumped with sequence valve18 in its initial setting. When that accumulated value reaches thepiggyback volume limit stored by pump control 94, a valve control signalis produced which causes sequence valve 18 to change state. Sequencevalve 18, in response to the valve control signal, occludes secondarytubing 40, and allows primary solution to flow through primary tubing30, to inlet tubing 22. Upon receiving the signal from sequence valve 18indicating that the change has been made, pump control 94 provides pumpdrive signals which cause pump drive motor 98 to operate at the pumpingrate selected for the primary solution. Pump control 94 again maintainsan accumulated value which represents the amount of primary solutionwhich has been pumped. This value is displayed on volume infused display86. When the accumulated value reaches the stored primary volume limit,pump control 94 halts operation of pump drive motor 98 and provides anindication through indicator panel 88 and audio annunciator 90 that boththe piggyback and primary administration have been completed. At thatpoint, the medical personnel responsible for the IV administration arerequired to intervene to set a new schedule of primary and piggybackrates and volume rates.

The present invention is advantageous because all of the medication fora single day or for several days can be stored in one large secondarybag 16, as opposed to such smaller secondary bags which run dry aftereach administration of that medication. For example, if a patient is toreceive 50 milliliters of secondary medication four times a day, fourbags would be required with the prior art systems, in which theswitching from the secondary bag to the primary solution is determinedby when the secondary bag is empty. With the system of the presentinvention, one 200 milliliter bag can be used for the entire day. Sincea large or a small bag costs essentially the same, there is a costsaving just by virtue of the reduced number of bags. In addition, thesystem significantly reduces the amount of time which is required ofmedical personnel. It is not necessary to change the secondary bag 16after each administration of medication, and in fact the presentinvention allows the secondary medication to be provided multiple timeswithout a change in the secondary bag.

By use of pump control 94 within housing 54 of pump 12 to controloperation of both pump 12 and sequence valve 18, the size, weight,complexity and cost of sequence valve 18 are significantly reduced. As aresult, sequence valve 18 can be suspended from the tubing (e.g. primarytubing 30) rather than requiring separate clamping to a pole. This makessequence valve 18 simpler and easier to use, and makes it portable sothat sequence valve 18 can be moved wherever pump 12 is moved.

FIGS. 4 through 7 show a first preferred embodiment of sequence valve18. FIG. 4 shows valve 18 in its normal initial operation position forpiggyback operation. As shown in FIG. 4, tubes 30 and 40 passside-by-side through valve 18. At the upper end, tubing 30 and tubing 40are retained by retainer spring 102, which has a pair of retainer arms102A and 102B. At the lower end, tubing 30 and tubing 40 are retained inside-by-side position by retaining FIGS. 104A and 104B of front cover106.

As shown in FIG. 4, lever 100 is in its uppermost ("cocked") position,which causes occluder stud 108 to be in its leftmost position. As aresult, primary tubing 30 is pinched off between occluder stud 108 andleaf spring 110. Also shown in phantom in FIG. 4 is the position oflever 100 and the position of occluder stud 108 after sequence valve 18has received a valve control signal from pump 12 which causes occluderstud 108 to move generally to the right to pinch off secondary tubing 40between occluder stud 108 and wall 112. Thus sequence valve 18 has twostable positions, one in which primary tubing 30 is occluded andsecondary tubing 40 is unoccluded; and the other in which secondarytubing 40 is occluded and primary tubing 30 is unoccluded.

FIG. 5 shows sequence valve 18 with front cover 106 removed. Theoperating mechanism of sequence valve 18 are supported by valve base114. Both occluder stud 108 and lever 100 are attached to bell crank116, which is pivotally mounted to valve base 114 by pivot pin 118.

As in FIG. 4, two positions of occluder stud 108 and the other movingparts of sequence valve 18 are shown. Solid lines represent the initialposition in which primary tubing 30 is occluded, and phantom linesillustrate the second position in which secondary tubing 40 is occluded.

Bell crank 116 is biased in a clockwise direction by bias spring 120,which is connected at its upper end to stud 12 and thus to valve base114, and which is connected at its lower end to stud 124 which projectsrearwardly from the lower end of bell crank 118.

Latch 126 is pivotally mounted about pivot pin 128, and has a latchtooth 130 which engages lower leg 132 of bell crank 116 when lever 100is in its cocked upper position. Latch arm 134 is held in the initialposition by solenoid plunger 136, which prevents rotation of latch 126about the axis defined by pivot pin 128.

Valve 18 will remain in a stable initial position until a valve controlsignal actuates solenoid 138 (FIG. 6). This causes solenoid plunger 136to be pulled in a rearward direction out of contact with arm 134 oflatch 126. This allows the bias force of spring 120 to rotate bell crank116 and in turn latch 126 about their respective pivot points 118 and128 to the position shown in phantom in FIG. 5. In the second stableposition of bell crank 116, leg 132 of bell crank 116 is located nearstop 140 (which limits rotation of bell crank 116 if secondary tubing 40is not in position to be pinched off). In this second stable state,occluder stud 108 is near its rightmost position, so that secondarytubing 40 is pinched off between occluder stud 108 and wall 112.

Sequence valve 18 is reset to its initial position by moving lever 100upward to the initial cocked position shown in solid lines. Latch spring142 urges latch 126 back to its initial position when sequence valve 18is being reinitialized. As shown in FIG. 6, rear surface 134A of arm 134is bevelled to form a ramp which allows arm 134 to move past solenoidplunger 136 as lever 100 is being cocked

Solenoid 138 includes a solenoid plunger stud 144 which extends out ofthe rear end of solenoid cover 146. At the rear end of solenoid plungerstud 144 is solenoid button 148. This button allows the nurse ortechnician to pull solenoid plunger 136 out of the way of latch 126 inorder to manually release lever 100, bell crank 116 and latch 126 fromthe cocked position. Button 148 can then be released and, due to thebias force of bias spring 150, solenoid plunger 136 returns to itsnormal position shown in FIG. 6.

It is also preferable for sequence valve 18 to provide an electricalsignal which indicates the current state of sequence valve 18. In theembodiment shown in FIG. 5, a metal contact stud 152 is attached to bellcrank 116. When valve 18 is in its initial state, contact stud 152 is incontact with contact wire 143. When the valve control signal has beenreceived and bell crank 116 has rotated to the position shown inphantom, contact stud 152 has moved into engagement with contact wire156. Depending upon which wire 154 or 156 is in contact with contactstud 152, a different electrical signal is supplied through cable 52 topump 12. This provides a simple, yet very effective way of indicatingthe state of sequence valve 18 to pump 12.

As shown in FIG. 7, upper retainer 102 is a single wire clip whichmounts over stud 158 at the upper end of valve base 114. The resilientnature of retainer 102 allows the retainer arms 102A and 102B to bedisplaced outwardly while tubing 30 and 40 are inserted into sequencevalve 18. Once released, arms 102A and 102B return to their normalposition shown in FIG. 7, thus securely holding tubing 30 and tubing 40in place.

Sequence valve 18 shown in FIGS. 4-7 is particularly advantageous, sinceit is small, light-weight (so that it can be supported on tubing 30 and40 without the need for a separate support stand) and uses a small,low-power solenoid. By using a pivoted latch 126 and a pivoted bellcrank 166, both of which provide a substantial mechanical advantage(e.g. 4:1 each), a very small movement of solenoid plunger 136 providesthe sufficient force to move occluder stud 108 to the right so as topinch off tubing 40. The force required to move solenoid plunger 136 isonly that necessary to overcome frictional force between latch 126 andsolenoid plunger 136. This frictional force is greatly reduced due tothe mechanical advantage provided by crank 116 and latch 126.

Sequence valve 18 shown in FIGS. 4-7 also uses an extremely simplemechanism to pinch off alternately either tubing 30 or tubing 40. By theuse of leaf spring 110 to urge tubing 30 toward occluder stud 108,sequence valve 18 does not require a precise alignment of both positionsof occluder stud 108, and variations in the diameters of tubing 30 and40 are accommodated. It is merely necessary to ensure that occluder stud108 moves far enough to the right to pinch off tubing 40 against theright wall 112 for the minimum expected diameter of tubing 40.

FIGS. 8-12 show a second embodiment of the sequence valve of the presentinvention. This second embodiment (which is designated valve 18') isgenerally similar to the embodiment of sequence valve 18 shown in FIGS.4-7, and similar reference numerals are used to designate similarelements. The internal operation of the bell crank, latch and solenoidof sequence valve 18' of FIGS. 8-12 are identical to those shown inFIGS. 4-7 and will not be discussed again.

The main difference between sequence valve 18' of FIGS. 8-12 andsequence valve 18 of FIGS. 4-7 is in the retaining of tubing 30 and 40.In sequence valve 18', a tube retainer 200 is pivotally mounted at theupper end of valve 18' between top end plate 202 and the upper ends offront cover 106 and valve base 114. Tube retainer 200 has a right leg204 which is pivotally mounted about pivot pin 206, a left leg 208, afront flange 210, and a tube hold-down flange 212. The closed positionof tube retainer 200 is shown in FIGS. 8-10, and the open position isshown in FIG. 11. Flange 210 forms a handle by which the nurse can pivottube retainer 200 to the open position to allow insertion or removal oftubing 30 and 40 from sequence valve 18'.

Left leg 208 of tube retainer 200 contains a hole 214 which receives aspring loaded ball 216 mounted in top plate 202 when tube retainer 200is in the closed position shown in FIGS. 8-10. Spring loaded ball 216maintains tube retainer 200 in the closed position and prevents it frommoving from the closed position if IV pump 12 or tubing 30 or 40 aremoved or bumped inadvertently.

Sequence valve 18' also used tube retainer 200 as a switch to indicateto pump that sequence valve 18' is in a condition to operate. For thispurpose, tube retainer 200 is an electrically conductive material,preferably metal. An electrically conductive washer 218, which ispartially shown in FIG. 11, is mounted on pivot pin 206 in contact withright leg 204 of tube retainer 200. Spring contact 200 is positioned sothat it will be engaged by left leg 208 when tube retainer 200 is in theclosed position. Thus when tube retainer 200 is in the closed position,a closed electrical path is provided between conductive washer 218 andspring contact 220.

FIG. 12 shows an electrical schematic diagram of sequence valve 18'. Inthis embodiment, cable 52 (which connects valve 18' to pump control 94)contains four wires 52A, 52B, 52C and 52D. Solenoid 138 is connected toground. When pump control 94 causes a voltage to be present betweenwires 52A and 52B, solenoid 138 is actuated.

Wires 52C and 52D are used to indicate to pump control 94 the conditionor state of sequence valve 18'. The switch formed by tube retainer 200,conductive washer 218 and spring contact 220 is connected in series witha switch formed by contact stud 152 and contact wires 154 and 156.Contact wire 154 is connected to wire 52D, and contact wire 156 isconnected to wire 52C.

If tube retainer 200 is in its open position, both wires 52C and 52Dwill indicate an open circuit. When tube retainer 200 is closed,normally one of the two wires 52C and 52D will be an open circuit, whilethe other will be connected to ground. By monitoring wires 52C and 52D,therefore, pump control 94 can determine the operating state of sequencevalve 18', as well as whether tube retainer 200 is in its closedposition.

FIGS. 8-11 also show retainer posts 222 and 224, which are positionedalong the channel, and which maintain tubing 30 and 40 in position alongthe entire length of the channel.

At the upper end of valve 18' is hook 226, which is attached by screw228 to top plate 202. Primary tubing 30 is threaded through hook 226 tomaintain sequence valve 18' in a generally vertical position. Thiscounteracts the tendency of the lower end of valve 18' to tip forwarddue to the greater weight of solenoid 138 within solenoid housing 146(see FIG. 6).

Also included in sequence valve 18' is a spring clip 230 and retainerpad 232 which are positioned along the left side of sequence valve 18'.Clip 230 allows sequence valve 18' to be clipped onto pump 12 when notin use. Pad 232 prevents sequence valve 18' from slipping when it isclipped onto pump 12.

FIGS. 13A-19C show a third embodiment of the sequence valve of thepresent invention. This third embodiment (which is designed valve 18")is generally similar to sequence valves 18 and 18' which have beendiscussed previously. Similar reference numerals are used to designatesimilar elements. Except as specifically discussed, the operation ofsequence valve 18" is generally similar to the operation of valves 18and 18', and not all elements of valve 18" will be discussed in detailfor that reason.

With the present invention, it is possible to provide multiple doses ofthe piggyback or secondary solution within secondary container 16.Typically, the secondary medication is intended to be provided to thepatient only in limited doses. Although secondary container 16 maycontain four or even six doses, it is important that a patient will notreceive multiple doses at one time due to malfunction or improper setup.The third embodiment of the present invention includes several featureswhich are specifically directed to preventing a dangerous situation inwhich multiple doses of the secondary solution are provided to thepatient at one time.

First, valve 18" includes features to prevent the nurse from reversingprimary tubing 30 and secondary tubing 40.

Second, sequence valve 18" is provided with several sensing mechanismsfor ensuring that the secondary tubing 40 is in position within sequencevalve 18 and is occluded when the sequence valve 18" switches state.

Third, sequence valve 18" also determines that bell crank 116 has movedwith a sufficient momentum to pinch off secondary tubing 40 whensequence valve 18" changes state.

To prevent reversal of the primary and secondary tubing 30 and 40,sequence valve 18 requires that tubing 30 and 40 be of different outerdiameters. Preferably, primary tubing 30 has a greater outer diameterthan secondary tubing 40. In one embodiment, the outside diameter ofprimary tubing 30 is 0.160 inches and the outer diameter of secondarytubing 40 is 0.125 inches.

As shown in FIGS. 13A-13D, 14A-14D and 15A-15D, sequence valve 18" has amain channel 240 formed in front cover 106 and top end cover 202 whichis divided into parallel primary and secondary channels 240A and 240B,respectively, which are of different size. At the upper end of channel240, semi-circular grooves 241 and 242 in top end plate 202 and frontplate 106, respectively, define the upper end of primary channel 240A.Secondary channel 240B is defined at the upper end of sequence valve 18"by semi-circular groove 243 in end cover 202 and semi-circular grooves244 and 246 in front cover 106. Grooves 241 and 243 are separated fromone another by rib 248 of end plate 202, and grooves 242 and 244 areseparated by rib 250 of front plate 106. Below the occluder studposition, rib 252 separates groove 246 from primary channel 240A. Nearthe bottom end of channel 240, retainer post 224 separates primary andsecondary channels 240A and 240B. Shoulder 254 is positioned oppositeretainer post 224 to narrow the width of secondary channel 240B.

When primary tube 30 is in position in primary channel 240A, it iscovered and held in position by control gate 256. At its lower end,control gate 256 is pivotally connected to front plate 106 by screw 258(see FIGS. 14B and 17) so that it pivots about axis 260 (see FIG. 16).

Control gate 256 has an upper arm 262 and a lower arm 264 for coveringthe front side of primary channel 240A when control gate 256 is closed.Upper arm 262 covers groove 242 between rib 250 and rib 266. Lower arm264 covers the portion of primary channel 240A between rib 252 and leafspring 110. Lower arm 264 has a first section 264A which is curved toavoid interference with leaf spring 110, and a second section 264B whichengages rib 252 and covers primary channel 240A.

Control gate 256 also includes a handle 268 to permit the operator tomove control gate 256 between its open and closed positions. As will bediscussed in further detail in conjunction with FIGS. 16-18, controlgate 256 also includes a leg 270 which has a notch 272. Leg 270 andnotch 272 cooperate with tooth 274 of bell crank 116 to ensure properpositioning of primary tube 30 and control gate 256 when lever 100 iscocked.

Tube retainer 200 includes an integral tube retainer insert 276 which isattached (such as by soldering) to the rear and bottom surfaces of tuberetainer 200. Retainer insert 276 has a first semi-circular section 278which covers groove 244, a second semi-circular section 280 which coversa portion of groove 246, and a third semi-circular section 282 whichcovers a portion of primary channel 240A between lower arm 264 ofcontrol gate 256 and occluder stud 108.

When tube retainer 200 is closed, therefore, it overlies the upper endsof primary and secondary channels 240A and 240B, as well as control gate256 to cause the upper ends of primary and secondary channels 240A and240B to be passageways of circular cross-section.

FIGS. 13A, 14A and 15A show the first step in the process of setting upsequence valve 18" for operation. In these three figures, both tuberetainer 200 and control gate 256 are open and neither primary tube 30nor secondary tube 40 have yet been inserted. Lever 100 is in itslowermost position, and occluder stud 108 is in its rightmost position.

In FIGS. 13B, 14B and 15B, primary tube 30 has been inserted and controlgate 256 has been closed. Tube retainer 200 remains open at this pointin the setup procedure.

In FIGS. 13C, 14C and 15C lever 100 has been cocked so that it is in itsuppermost position and occluder stud 108 has moved to its leftmostposition. As a result, primary tube 30 is pinched off between occluderstud 108 and leaf spring 110. Secondary tubing 40 is then inserted inchannel 240B.

In FIGS. 13D, 14D and 15D, tube retainer 200 has been closed. At thispoint, sequence valve 18" is ready to begin operation.

Because of the difference in size of primary channel 240A and secondarychannel 240B, it is not possible to reverse the positions of primarytubing 30 and secondary tubing 40. Although secondary tubing 40 could beplaced in primary chanel 240A, primary tubing 30 is too large to fit insecondary channel 240B. This will become immediately apparent to thenurse, who will be unable to insert primary tubing 30 into secondarychannel 240B, and will be unable to close tube retainer 200. The use oftwo different sized channels 240A and 240B, therefore, provides asimple, yet extremely effective, method for preventing an erroneousreversal of the primary tubing 30 and secondary tubing 40 within valve18".

FIGS. 16-18 illustrate the interaction of bell crank 116 and controlgate 256. Leg 270 of control gate 256 travels along a path whichintersects the path of tooth 274 of bell crank 116. As a result, ifcontrol gate 256 is open and lever 100 is cocked to its uppermostposition, tooth 274 is in its leftmost position which blocks the path ofleg 270. As a result, control gate 256 cannot be closed if lever 100 hasbeen cocked first. If control gate 256 cannot be closed, tube retainer200 also cannot be closed because control gate 256 is in the way. Ths isa clear indication to the nurse who is setting up sequence valve 18"that the proper setup sequence has not been followed. In addition, theswitch formed by tube retainer 200 is not closed, and pump 10 will notoperate. The nurse must then pull on solenoid release knob 148 torelease bell crank 116 and start the setup sequence again.

If control gate 256 is only partially closed and the nurse attempts tocock lever 100, leg 270 will be positioned in the path of tooth 274.Thus it will not be possible to cock lever 100 when control gate 256 ispartially closed.

The proper time for cocking lever 100 is when primary tube 30 is inprimary channel 240A and control gate 256 is closed. Under thoseconditions, notch 272 is aligned with the path of tooth 274, so thatbell crank 116 can pivot to the cocked position shown in FIG. 18. Inthis position, tooth 274 projects through notch 272, thus preventingcontrol gate 256 from being opened as long as lever 100 is cocked. Thisprevents any inadvertent or deliberate attempt to remove primary tube 30from primary channel 240A as long as lever 100 is cocked.

During setup of an IV administration system, it is common for some ofthe IV fluid to be spilled. The primary solution generally is a glucosesolution, which when it dries is sticky and can interfere with theproper operation of moving parts. Of particular concern is the propermovement of bell crank 116 and occluder stud 108 so that secondarytubing 40 is pinched off when the valve changes state. This is ofcritical importance, since incomplete occlusion could allow an overdoseof the secondary fluid to be pumped to the patient, with potentiallydangerous results.

In a preferred embodiment of the present invention shown in FIGS.19A-19C, contact wires 54 and 56 are provided to indicate the positionof bell crank 116. The circuit shown schematically in FIGS. 19A-19C isgenerally similar to the circuit shown in FIG. 5, and similar referencecharacters are used to designate similar elements. Contact stud 152 isprovided on bell crank 116 for contacting contact wires 154 and 156.When lever 100 is in its cocked position, contact stud 152 is in contactwith wire 154 as shown in FIG. 19A. When valve 18" is actuated, bellcrank 116 moves toward its uncocked position, and contact stud 152contacts wire 156 (FIG. 19B).

Occluder stud 108 will contact secondary tubing 40 before bell crank 116reaches its fully uncocked position. In one embodiment, the distancefrom the occluder stud 108 to the right wall of secondary channel 240Bis 0.053 inches when the occluder stud contact 152 makes contact withwire 156. The rest position of occluder stud 108 to the right wall ofsecondary channel 240B which produces occlusion of tubing 40 is 0.033inches. If no tube is present in secondary channel 240B, the distancefrom the occluder stud 108 to the right wall of the secondary channel240B is 0.010 inches.

In a preferred embodiment of the present invention, contact wire 156 ispositioned to sense when bell crank 116 has reached a point whereoccluder stud 108 begins to contact secondary tubing 40. This does not,however, provide an absolute indication that bell crank 116 is movingwith sufficient force to be able to fully occlude secondary tubing 40.For example, if the sequence valve 18" has become exposed to glucosesolution, bell crank 116 may be moving so slowly that it does not havesufficient momentum to carry it through to final position which fullyoccludes secondary tubing 40. To detect this potential error condition,pump control 94 (FIG. 3) senses the time from when contact stud 152breaks contact with contact wire 154 until is makes contact with contactwire 156. If that measured time is less than a predetermined value, itindicates that the bell crank 116 is moving with sufficient velocity andhas sufficient momentum to fully occlude tubing 40. If, on the otherhand, contact is never made with contact wire 156, or the time intervalis greater than the predetermined value, an alarm is provided, sincethis indicates that bell crank 116 may not have sufficient momentum toocclude secondary tubing 40.

As shown in FIGS. 19A-19C, contact wire 156 is fixed at one end and freeat its opposite end. If secondary tubing 40 is not in channel 240B,contact stud 152 applies force to contact wire 156 which bends contactwire 156 around fixed post 284 (FIG. 19C). This causes the free end ofcontact wire 156 to break contact with terminal 286. As a result, thesignal on wire 52C will go from high (FIG. 19A) to low (FIG. 19B) tohigh (FIG. 19C) if secondary tubing 40 is not in channel 240B. Bymonitoring the signal transitions on lines 52C and 52D, therefore, pumpcontrol 94 can determine the existence of a potential error conditionand provide an alarm through annunciator 90.

FIG. 20 shows still another improvement to the sequence valve 18" of thepresent invention. In this modified embodiment, a second leaf spring 288is located along the right hand side of secondary channel 240B. Leafspring 288 cooperates with occluder stud 108 to pinch off secondarytubing 40 when valve 18" is actuated. Leaf spring 288 provides a greateramount of tolerance in positioning, and also allows a slight amount of"give" as occluder stud 108 moves toward secondary tubing 40.

Leaf spring 288 allows contact wire 156 to be positioned at the pointwhere occlusion of secondary tubing 40 normally takes place. Spring 288is stiff enough to allow secondary tubing 40 to be pinched off betweenoccluder stud 108 and spring 288, yet allows a slight amount ofover-travel of occluder stud 108 beyond the point at which occlusionfirst occurs. As a result, contact wire 156 can be positioned at thepoint where occlusion initially takes place, with assurance thatoccluder stud 108 will actually move slightly past that position.

In contrast, when the right hand side of secondary channel 240B is fixed(as in the other embodiments of the present invention), contact wire 156must be placed at a position slightly before occlusion normally takesplace. Otherwise, a slight variation in wall thickness or otherdimension of the secondary tubing 40 can result in a failure of contactstud 152 to make contact with contact wire 156 and thus cause a nuisancealarm.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, although the present inventionhas been described in the context of a system in which a primary andonly one secondary bag are used, it is also applicable to more complexsystems in which multiple secondary bags are used in conjunction with aprimary bag.

Similarly, although the present invention has been described in thecontext of a specific type of IV pump, the present invention isapplicable to other IV pump and controller systems as well.

What is claimed is:
 1. A sequence valve for selectively occluding firstand second flexible tubes in sequence, the sequence valvecomprising:housing means which includes a base and channel means forpositioning the first and second tubes in side-by-side relationship;crank means pivotally connected to the base for movement about a firstpivot axis along a first path between first and second crank positions;bias means for providing a bias force to the crank which urges the cranktoward the second crank position; occluder means connected to the crankfor occluding the first flexible tube when the crank is in the firstcrank position, and for occluding the second flexible tube when thecrank is in the second crank position; releasable latch means supportedby the housing for latching the crank in the first crank position andfor releasing the crank in response to a control signal to allow thebias force to pivot the crank to the second crank position; tuberetainer means positioned adjacent the channel means and pivotallyconnected to the housing for pivoting about a second pivot axis along asecond path between an open position in which tubes can be inserted intoor removed from the channel means and a closed position which holds thetubes in the channel means; gate means pivotally connected to thehousing for pivoting about a third pivot axis along a third path betweenan open position in which the first tube can be inserted into or removedfrom the channel means, and a closed position which holds the first tubechannel means; and wherein the second and third pivot axes arepositioned so that the gate means and the tube retainer means haveintersecting paths, and the gate means includes means for preventing thetube retainer means from moving along the second path to its closedposition unless the gate is in its closed position.
 2. The sequencevalve of claim 1 and further comprising:means for providing a signalwhich indicates whether the tube retainer is in its closed position. 3.The sequence valve of claim 1 wherein the first, second and third pathslie in first, second and third generally orthogonal planes,respectively.
 4. A sequence valve for selectively occluding first andsecond flexible tubes in sequence, the sequence valve comprising:housingmeans which includes a base and channel means for positioning the firstand second tubes in side-by-side relationship; crank means pivotallyconnected to the base for movement about a first pivot axis along afirst path between first and second crank positions; bias means forproviding a bias force to the crank which urges the crank toward thesecond crank position; occluder means connected to the crank foroccluding the first flexible tube when the crank is in the first crankposition, and for occluding the second flexible tube when the crank isin the second crank position; releasable latch means supported by thehousing for latching the crank in the first crank position and forreleasing the crank in response to a control signal to allow the biasforce to pivot the crank to the second crank position; tube retainermeans positioned adjacent the channel means and pivotally connected tothe housing for pivoting about a second pivot axis along a second pathbetween an open position in which tubes can be inserted into or removedfrom the channel means and a closed position which holds the tubes inthe channel means; gate means pivotally connected to the housing forpivoting about a third pivot axis along a third path between an openposition in which the first tube can be inserted into or removed fromthe channel means, and a closed position which holds the first tube inthe channel means; and wherein the crank means includes means forblocking movement of the gate means along the third path to its closedposition when the crank means is in the first crank position.
 5. Asequence valve for selectively occluding first and second flxible tubesin sequence, the sequence valve comprising:housing means which includesa base and channel means for positioning the first and second tubes inside-by-side relationship; crank means pivotally connected to the basefor movement about a first pivot axis along a first path between firstand second crank positions; bias means for providing a bias force to thecrank which urges the crank toward the second crank position; occludermeans connected to the crank for occluding the first flexible tube whenthe crank is in the first crank position, and for occluding the secondflexible tube when the crank is in the second crank position; releasablelatch means supported by the housing for latching the crank in the firstcrank position and for releasing the crank in response to a controlsignal to allow the bias force to pivot the crank to the second crankposition; tube retainer means positioned adjacent the channel means andpivotally connected to the housing for pivoting about a second pivotaxis along a second path between an open position in which tubes can beinserted into or removed from the channel means and a closed positionwhich holds the tubes in the channel means; gate means pivotallyconnected to the housing for pivoting about a third pivot axis along athird path between an open position in which the first tube can beinserted into or removed from the channel means, and a closed positionwhich holds the first tube in the channel means; and wherein the crankmeans includes means for blocking movement of the gate means along thethird path from its closed position when the crank means is in the firstcrank position.
 6. A sequence valve for selectively occluding first andsecond flexible tubes in sequence, the sequence valve comprising:housingmeans which includes a base and channel means for positioning the firstand second tubes in side-by-side relationship; crank means pivotallyconnected to the base for movement about a first pivot axis along afirst path between first and second crank positions; bias means forproviding a bias force to the crank which urges the crank toward thesecond crank position; occluder means connected to the crank foroccluding the first flexible tube when the crank is in the first crankposition, and for occluding the second flexible tube when the crank isin the second crank position; releasable latch means supported by thehousing for latching the crank in the first crank position and forreleasing the crank in response to a control signal to allow the biasforce to pivot the crank to the second crank position; tube retainermeans positioned adjacent the channel means and pivotally connected tothe housing for pivoting about a second pivot axis along a second pathbetween an open position in which tubes can be inserted into or removedfrom the channel means and a closed position which holds the tubes inthe channel means; gate means pivotally connected to the housing forpivoting about a third pivot axis along a third path between an openposition in which the first tube can be inserted into or removed fromthe channel means, and a closed position which holds the first tube inthe channel means; and wherein the gate means includes means forblocking movement of the crank means along the first path to the firstcrank position when the gate means is in a position along its third pathbetween its open and closed positions.
 7. A sequence valve forselectively occluding first and second flexible tubes in sequence, thesequence valve comprising:housing means including channel means in whichthe tubes are positioned in side-by-side relationship; pivotable crankmeans connected to the housing means for pivotal movement about a firstpivot axis along a first path; occluder means connected to the crankmeans for pinching off one of the first and second tubes depending uponthe position of the crank means, wherein the occluder means extends intothe channel means between the first and second tubes and is movable in agenerally transverse direction as the crank means moves along the firstpath; bias spring means for applying a bias force to the crank means;tube retainer means connected to the housing means and positionedadjacent a first end of the channel means for pivoting about a secondaxis along a second path between an open position in which tubes can beinserted into or removed from the channel means and a closed positionwhich holds the tubes in the channel means; gate means connected to thehousing means for pivotong about a third axis along a third path betweenan open position in which the first tube can be inserted into or removedfrom the channel means, and a closed position which holds the first tubein the channel means; pivotable latch means connected to the housing forholding the crank means in a position in which the fist tube is pinchedoff; solenoid means which releases the latch means in response to acontrol signal to permit the latch means to pivot out of engagement withthe crank means and thereby allow the bias force to pivot the crankmeans to a position in which the second tube is pinched off; and means,carried by at least one of the crank means, the tube retainer means, andthe gate means, for requiring sequential movement of the crank means,the tube retainer means and the gate means during loading and unloadingof the tubes to and from the channel means.
 8. The sequence valve ofclaim 7 wherein the means for requiring sequential movement includesmeans for preventing the tube retainer means from moving along thesecond path to its closed position unless the gate means is in itsclosed position.
 9. The sequence valve of claim 7 wherein the means forrequiring sequential movement includes means for preventing movement ofthe gate means along the third path to and from its closed position whenthe crank means is in the position in which the first tube is pinchedoff.
 10. The sequence valve of claim 7 wherein the means for requiringsequential movement includes means for preventing movement of the crankmeans along the first path to the position in which the first tube ispinched off when the gate means is between its open and closedpositions.
 11. The sequence valve of claim 7 wherein the first, secondand third paths lie in first, second and third generally orthogonalplanes, respectively.
 12. An IV administration system comprising:a firstsource of a first IV fluid; a second source of a second IV fluid; an IVcontrol device having an inlet and an outlet for delivering IV fluids; afirst flexible tube connected between the first source and the inlet; asecond flexible tube connected between the second source and the inlet;a sequence valve positioned between the first and second sources and theinlet for selectively occluding the first and second flexible tubes insequence, the sequence valve comprising:a base having channel means forreceiving the first and second flexible tubes; crank means pivotallyconnected to the base for movment about a first pivot axis along a firstpath between first and second crank positions; bias means for providinga bias force to the crank means which urges the crank means toward thesecond crank position; occluder means connected to a first end of thecrank means for occluding the first flexible tube when the crank meansis in the first crank position, and for occluding the second flexibletube when the crank means is in the second crank position; releasablelatch means connected to the base for latching the crank means in thefirst crank position and for releasing the crank means in response to acontrol signal to allow the bias force to pivot the crank means to thesecond crank position; tube retainer means connected to the base forpivoting about a second axis along a second path between an openposition in which tubes can be inserted into or removed from the channeland a closed position which holds the tubes in the channel means; andgate means for pivoting about a third axis along a third path between anopen position in which the first tube can be inserted into or removedfrom the channel means, and a closed position which holds the first tubein the channel means where the first, second and third axes arepositioned so that at least two of the first, second and third pathsintersect, wherein the gate means includes means for preventing the tuberetainer means from moving along the second path to its closed positionunless the gate means is in its closed position; and means for providingthe control signal to the sequence valve.
 13. The system of claim 12 andfurther comprising:means for providing a signal which indicates whetherthe tube retainer is in its closed position.
 14. The system of claim 12wherein the occluder means comprises an occluder stud connected to thecrank and extending into the channel means between the first and secondtubes so that when the crank is in the first crank position the occluderstud causes the first tube to be pinched off and when the crank is inthe second crank position the occluder stud causes the second tube to bepinched off.
 15. The system of claim 12 wherein the first and secondflexible tubes have different diameters and wherein the channel meansdefines first and second channels having different dimensions related tothe different diameters so that the first and second flexible tubescannot be reversed with the first tube in the second channel and thesecond tube in the first channel.
 16. The sequence valve of claim 12wherein the first, second and third paths lie in first, second and thirdgenerally orthogonal planes, respectively.
 17. An IV administrationsystem comprising:a first source of a first IV fluid; a second source ofa second IV fluid; an IV control device having an inlet and an outletfor delivering IV fluids; a first flexible tube connected between thefirst source and the inlet; a second flexible tube connected between thesecond source and the inlet; a sequence valve positioned between thefirst and second sources and the inlet for selectively occluding thefirst and second flexible tubes in sequence, the sequence valvecomprising:a base having channel means for receiving the first andsecond flexible tubes; crank means pivotally connected to the base formovement about a first pivot axis along a first path between first andsecond crank positions; bias means for providing a bias force to thecrank means which urges the crank means toward the second crankposition; occluder means connected to a first end of the crank means foroccluding the first flexible tube when the crank means is in the firstcrank position, and for occluding the second flexible tube when thecrank means is in the second crank position; releasable latch meansconnected to the base for latching the crank means in the first crankposition and for releasing the crank means in response to a controlsignal to allow the bias force to pivot the crank means to the secondcrank position; tube retainer means connected to the base for pivotingabout a second axis along a second path between an open position inwhich tubes can be inserted into or removed from the channel and aclosed position which holds the tubes in the channel means; and gatemeans for pivoting about a third axis along a third path between an openposition in which the first tube can be inserted into or removed fromthe channel means, and a closed position which holds the first tube inthe channel means wherein the first, second and third axes arepositioned so that at least two of the first, second and third pathsintersect; and wherein the crank means includes means for blockingmovement of the gate means along the third path to and from its closedposition when the crank means is in the first position.
 18. An IVadministration system comprising:a first source of a first IV fluid; asecond source of a second IV fluid; an IV control device having an inletand an outlet for delivering IV fluids; a first flexible tube connectedbetween the first source and the inlet; a second flexible tube connectedbetween the second source and the inlet; a sequence valve positionedbetween the first and second sources and the inlet for selectivelyoccluding the first and second flexible tubes in sequence, the sequencevalve comprising: a base having channel means for receiving the firstand second flexible tubes;crank means pivotally connected to the basefor movement about a first pivot axis along a first path between firstand second crank positions; bias means for providing a bias force to thecrank means which urges the crank means toward the second crankposition; occluder means connected to a first end of the crank means foroccluding the first flexible tube when the crank means is in the firstcrank position, and for occluding the second flexible tube when thecrank means is in the second crank position; releasable latch meansconnected to the base for latching the crank means in the first crankposition and for releasing the crank means in response to a controlsignal to allow the bias force to pivot the crank means to the secondcrank position; tube retainer means connected to the base for pivotingabout a second axis along a second path between an open position inwhich tubes can be inserted into or removed from the channel and aclosed position which holds the tubes in the channel means; and gatemeans for pivoting about a third axis along a third path between an openposition in which the first tube can be inserted into or removed fromthe channel means, and a closed position which holds the first tube inthe channel means wherein the first, second and third axes arepositioned so that at least two of the first, second and third pathsintersect; and wherein the gate means includes means for blockingmovement of the first crank means along the first path to the firstcrank position when the gate means is between its open and closedpositions.
 19. An IV administration system comprising:a first source ofa first IV fluid; a second source of a second IV fluid; an IV controldevice having an inlet and an outlet for delivering IV fluids; a firstflexible tube having a first outside diameter connected between thesource and the inlet; a second flexible tube having a second, differentoutside diameter connected between the second source and the inlet; asequence valve positioned between the first and second sources and theinlet for pinching off the first tube and then the second tube insequence, the sequence valve comprising:spring biased pivotable tubepincher means supported by the housing and positioned for pinching offthe first and then the second tube. pivotable latch means supported bythe housing for holding the tube pincher means in a position in whichthe first tube is pinched off; solenoid means supported by the housingmeans which releases the latch means in response to a control signal topermit the latch means to pivot out of engagement with the tube pinchermeans and thereby allow the tube pincher means to pivot in a position inwhich the second tube is pinched off; first and second channels in thehousing means for receiving and holding the first and second tubes,respectively, in positions where they can be pinched off by the tubepincher means, one of the channels having a dimension which is sized toreceive only the tube having the smaller outside diameter so that thefirst and second flexible tubes cannot be reversed with the first tubein the second channel and the second tube in the first channel; andmeans supported by the housing means for pivoting between an openposition in which the tubes can be inserted into and removed from thechannels and a closed position which holds the tubes in the channels,and including means for preventing movement of the tube pincher meansunless the means for pivoting is at one of its open and closedpositions; and means for providing the control signal to the sequencevalve.